Regenerative medicine, mainly utilizing stem cells, has considerably progressed in recent years. Various tissue stem cells, which had not been considered to be present, were discovered and identified in various tissues. Thus, attention has been focused on disease therapy using (regenerative therapy).
However, regenerative therapy has not yet reached a point where it is conventionally applied to numerous patients suffering from organ or tissue dysfunction. To date, a very limited number of such patients have been treated by organ transplantation or use of an auxiliary medical system or apparatus. These therapies are problematic in shortage of donors, rejection, infection, durability, and the like. Particularly, the donor shortage raises serious problems. In the case of bone marrow transplantation, bone marrow and umbilical cord blood banks have gradually become more widely used home and abroad, though it is still difficult to provide a limited amount of samples to a number of patients. Therefore, there is an increasing demand for therapies using stem cells and regenerative medicine using the same in order to overcome the above-described problems. Use of foreign tissue for organ implantation (e.g., heart, blood vessels, etc.) is hindered mainly by immune rejection responses. Changes occurring in allogenic grafts (or allografts) and xenografts are well known.
After gastrulation, a fertilized egg is divided into three germ layers, i.e., endoderm, mesoderm, and ectoderm. Cells derived from the ectoderm are mainly present in brain, including neural stem cells and the like. Cells derived from the mesoderm are mainly present in bone marrow, including blood vessel stem cells, hematopoietic stem cells, mesenchymal stem cells, and the like. Cells derived from the endoderm are mainly present in organs, including liver stem cells, pancreatic stem cells, and the like.
Mesenchymal cells, such as adipocytes, bones, ligaments, cardiac muscles, and the like, have an important function of forming the shape or skeleton of the body. Therefore, there is an increasing expectation for the application of groups or tissues of such cell store generative medicine and implantation medicine. Particularly, it has been reported that bone marrow mesenchymal stem cells can be differentiated into mesodermal organs, and such stem cells have attracted attention mainly in the field of regenerative medicine. However, differentiation of such cells requires special conditions where a special medium containing a differentiation inducing agent (e.g., dexamethasone, etc) is required (Nakatsuji, ed., “Kansaibo Kuron Kenkyu Purotokoru [Stem cell/Clone Research Protocol]”, Yodosha (2001)).
Mesenchymal stem cells are a type of tissue stem cells. Mesenchymal stem cells naturally occur only in a small amount (one ten thousandth of all cells in the bone marrow of human neonates, thereafter reducing quickly, and one two millionth of all cells in elderly persons). It is therefore difficult to isolate mesenchymal stem cells. As it has been reported that mesenchymal stem cells are differentiated into germ layers other than mesoderm, the range of applications is becoming widespread. However, conditions for such differentiation are more specific than those which are described above. The known surface antigens of mesenchymal stem cells are CD105(+), CD73(+), CD29(+), CD44(+), CD14(−), CD34(−), and CD45(−).
On the other hand, it has been found that fat contains stem cells (WO00/53795; WO03/022988; WO01/62901; Zuk, P. A., et al., Tissue Engineering, Vol. 7, 211-228, 2001; Zuk, P. A., et al., Molecular Biology of the Cell, Vol. 13, 4279-4295, 2002). Fat supplies a larger amount of stem cells than other tissues (e.g., bone marrow, etc.) and the density of stem cells seems to be higher. Therefore, fat has attracted attention. However, methods for treating stem cells are not fully understood.
For bone marrow-derived stem cells, various methods for inducing the cells to differentiate to target cells in vitro are known (WO96/39035, WO97/41208, WO99/64565, WO97/40137, and WO00/06701). It has been demonstrated that in vitro induction of differentiation can be performed with a method similar to that for bone marrow-derived mesenchymal stem cells. However, there has been no such report for adipose-derived precursor cells. In addition, there has been no report known for in vivo induction of differentiation. The destiny of a tissue stem cell is determined to some degree by its origin. It is believed that even if stem cells are treated under the same conditions, the level of differentiation differs from tissue stem cell to tissue stem cell. Attempts have been made to utilize adipocytes in medicine (Japanese Laid-Open Publication No. 2001-103963, Japanese Laid-Open Publication No. 2001-103965, and WO99/28444), but there has been no report for clinical trials of adipose-derived precursor cells.
Alternatively, a cosmetic therapy has been practiced, in which fat is removed and transplanted. In this method, however, it is difficult to obtain a desired shape and a satisfactory level of affinity. It cannot be said that the desired result of cosmetic surgery is obtained. Therefore, there is a demand for a surgical method for obtaining a desired cosmetic effect and a material or medicament for use in such a method.
Thus, there is an increasing demand for a simple method for controlled differentiation of adipose-derived precursor cells in the art. An object of the present invention is to meet such a demand. An other object of the present invention is to provide a clinical method for obtaining a desired cosmetic effect and a material or medicament for use in such a method.